(Bloomberg View) -- Hillary Clinton supports adding a public option to the Affordable Care Act -- that is, a government-run insurance program to compete with private health insurance.

She announced her support in July, and the public option was the only specific change to Obamacare that she mentioned in her economics speech last week.

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This position makes a lot of practical sense, as the New Republic’s Brian Beutler has been pointing out. The Congressional Budget Office has scored a public option as deficit-reducing, which means Democrats wouldn't have to raise taxes or cut spending to pay for it. A public option has also polled well. For example, back in December 2009 a CBS News/New York Times survey found 59 percent favored including a public option in Obamacare, with only 29 percent opposed.

It was a big disappointment to liberals during the 2009-2010 legislative fight over the ACA when the public option disappeared from the bill. So it would seem to be a logical next step for liberal politicians seeking to improve Obamacare.

But it's one thing for Democrats to support a policy. It's quite another for it to be the kind of high priority they would fight for.

Parties have many more goals than they'll ever have the opportunities to enact, even if they win large victories. Getting bills through Congress is hard, even if majorities in both chambers favor a measure.

So especially for a major proposal such as the public option, the question isn't whether the party supports it. It's how much.

Unfortunately for public-option advocates, the candidates most likely to become new Democratic senators in 2017 don't seem especially interested in advocating that policy.

Only one of 11 candidates, Chris Van Hollen of Maryland, mentions support for a public option on the issues section of his campaign website. Indeed, only six of the 11 that I surveyed even had a “health care” section on their websites. Kamala Harris, in solidly Democratic California, has nine different subject areas, from immigration to the environment and “protecting animals.” She has separate tabs for higher education and K-12 education. But no health care.

Sure, given the opportunity, the Democrats might move some relatively uncontroversial or small health-care measures. But their campaign messages suggest that they may not be up to a battle over consequential health-care legislation, which is what a push for a public option would be. 

That doesn't mean it won't happen. Some of these candidates won’t even be elected. Incumbent senators may have different priorities. And some of these candidates may yet add a ringing endorsement of the public option before the election. 

But if Democratic party actors were demanding a public option, campaigns would have highlighted it in their campaign materials. Indeed, candidates with tough primaries such as Katie McGinty in Pennsylvania or Patrick Murphy in Florida (whose primary is still to come), might well have become vocal champions of the public option. They didn't.

Campaigns are as much about choosing priorities as they are about choosing policies. Clinton has clearly committed to adding a public option to Obamacare -- but she’s also committed to dozens of other positions. If it isn’t a priority for the rest of the party, it won’t be a priority for her either. 

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